Now You See Me, Now You Don't: The Road to Invisibility

Author:  Schuck Kirsten
Date:  October 2006

Out of Fiction and into Reality

At one time, it seemed like invisibility was a notion of science fiction, purely based on imagination, but today it seems we may be close to making that fantasy a reality. Scientists have identified a way to make an invisibility cloak (yes, just like the one in Harry Potter) which could render its wearer invisible. This cloak would use a revolutionary material and could literally change the way we see the world.

The Invisibility Team

Physicists and engineers have come together from across the world to work on this project. So far, invisibility cloaks are in the works in both Japan and in the US. Some of the pioneers of this invisibility cloak include David Schurig and David R. Smith, from Duke University's Pratt School of Engineering, and John Pendry of Imperial College London. The scientists have published their work in the journal Science, and their research is supported by the Defense Advanced Projects Research agency.

These researchers have been working with new materials called "metamaterials". Metamaterials are artificially created materials that are unique because they have gain different properties based on the shape they take, rather than from their composition. This allows the cloak to react to light very differently than ordinary objects,

How it Works

Light flow around an object, concealing the object within. Image courtesy of

Light flow around an object, concealing the object within. Image courtesy of

Working with these materials, the researchers have been able to create what is best described as a black hole in space. Scientists compare the cloak to a rock in a running stream--the water flows right around the rock and comes back together on the other side as if it was never obstructed. The cloak acts in the same way, allowing the light to flow around it and enabling the person or object inside to "disappear".

Light travels in a straight line because, as defined in Fermat's principle, it is the shortest distance between two points. If space is curved, then the shortest distance between two points is a curve. When the invisibility cloak is used, the space is pushed out as if we were transforming space and distorting the way light moves. Light travels directly around the object and acts as though there was no object there when it comes back together.

According to a Professor Smith, "All light or other electromagnetic waves are swept around the area, guided by the metamaterial to emerge on the other side as if they had passed through an empty volume of space."

In order to test the effectiveness of the cloak, scientists use a method called ray-tracing. In this method, rays act like light and can be observed as they pass through or around an object. This allows the scientists to double check the material's measurements to see that they are all correct. The ideal invisibility cloak would be made of transparent material, capable of bending light around an object concealed behind it. Although the cloak would completely conceal any object, it would also keep the person and or object from having any view of the area surrounding the cloak.

Why Be Invisible?

While fiction writers and Hollywood have promoted other ways of attaining invisibility, using metamaterials to create an invisibility cloak has, to date, proven to be the only viable option. Very often innovation draws from fictional inspiration, and writers have obscured many scientific ideas for their own fictional ends. But the new invisibility cloaks now being designed have some real-world applications.

Invisibility has been explored in venues such as comic books, and movies, written as a superhuman power that was present only in the fantasy world. The creators of these works have no constraints besides those of their own imaginations, but scientists are restrained by the laws governing science and nature. There have been many ideas presented that were thought to be outside the realm of science, but today we see the ideas of the future slowly becoming reality.

Scientists predict that the cloak may be useful in defense; hiding objects that we do not want other agencies or countries to see. The cloak may also offer options for improving wireless communications because it would allow obstructions to be removed from the path of wireless communication. While the idea of invisibility may seem ominous and impractical to some, the investigators of this subject offer some uses for the cloak. They also propose the use of this cloak to alleviate unsightly buildings or structures which may obscure someone's beautiful view.

As technology increases so do the ideas for uses of the invisibility cloak. The idea of invisibility was once just a figment of our imagination, but we are coming closer and closer to integrating fantasy into our reality. From robots, to hybrid cars, to invisibility, this research just proves that we can put our ideas into action.